Charli XCX and Troye Sivan bask in Nineties nostalgia for their bouncy new single “1999.” The song is the pair’s first collaboration together.

On the referential tune, the pair look back on the year 1999 and reminisce about how much easier life was for them that year. “I just wanna go back/Sing ‘Hit Me Baby One More Time,'” they sing on the upbeat chorus, between references to MTV, their budding sexual awakenings and their childhood homes.

Charli XCX has spent the past several months opening for Taylor Swift on her Reputation World Tour. The North American leg wrapped this week, and the tour itself will continue in a week with shows in Australia, New Zealand and Japan. XCX’s last full-length album was 2014’s Sucker. She has released two acclaimed mixtapes since then, including the December release Pop 2. While on tour with Swift, she has released several new singles including the long-teased “Girls Night Out.”